Introduction:

Switches turn circuits on and off. Some of the most interesting switches are the kind that operate automatically. For example, a thermostat will automatically turn the furnace on when the temperature gets too low. A refrigerator will automatically turn the chiller on when the temperature gets too high.

Activity:

• Get the document D1 Temperature Switch from your iCal. Construct the circuit as shown, capture the image into your ComicLife document, PDF it, and submit it to the Hand-in Robot.
• Try the quiz D2, linked to your iCal, or to the icon on the right.

Practice:

Read the following story, and design a circuit that would do the job!
I have the strangest dog. Her name is Regi. When I am not home, at least according to the neighbors, she never barks. When I am home, though, there are lots of situations that get her barking. If a cat or a squirrel walks by, she barks. If the doorbell rings when we are home, she barks. If the phone rings, she will bark if I am asleep, but not if I am awake. If she is hungry and the bowl is empty, she will bark.

Now, I have never been a big fan of barking dogs. But my dog is getting old, and I will miss her when she is gone. I'd like someone to help me make a robotic dog to replace her. Let's assume that we can create sensors for each condition that affects my real-live dog. How would you connect these sensors to a battery-operated barking machine, so that it would react like Regi does?

Start by picking one "barking scenario" and designing that circuit, and then building up from there! When you are done, we will share the circuit with the class.